Anti-block edge for plastic bags and the like



Dec. 10, 1963 e. D. PANGRAC 3,7

ANTI-BLOCK EDGE FOR PLASTIC BAGS AND THE LIKE Filed Feb. 3, 1961 INVEN TOR. Georye 0. Pang rac BY W912i a 7 United rates Patent Q 3,113,715 ANTl-Blfifii EDGE FGR PLAS'HC BAKE AND THE LEKE George D. Pangrac, North @lrnsted, @hio, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed Feb. 3, 1951, Ser. No. 86,957 3 fiaims. (Cl. 229-53) The chief aim and design of this invention is to provide a better and more satisfactory edge or lip at the opening in a plastic bag, sack, pouch or the like closure or construction, which edge has greatly minimized, if not entirely avoided, tendency to block upon and adhere to the opposite edge in the opening during separating operations on the opening.

All smooth surfaces basically tend to adhere to each other when in intimate, fiatly disposed contact. This is particularly the case with plastic film, such as polyethylene, polypropylene and the like or equivalent thermoplastic resinous materials (especially polyolefins), used for and in bags, sleeves and the like constructions in which there is provided an opening for access formed by (or with) joinable edges or lips in the construction that are adapted to lie flatly upon and against one another when the bag is closed (especially when empty). This phenomenon makes the opening of a plastic film bag or the like difficult and frequently troublesome, especially during mechanical filling and other handling manipulations.

Now, however, by practice of this invention, there is an easy and effective way to overcome and avoid such dificulties in good quality and highly satisfactory plastic bags and the like.

In order to do this and get the many benefits and advantages of following this invention, a laterally extending, linearly protuberant physical deformation, which may be either a wave (or curl or scallop) or an even bead, is located at and along at least one of the edges or lips of the opening in a plastic bag or the like article.

All this is shown better in the drawing, in which:

FIGURE 1 is a grossly exaggerated fragmentary crosssectional view through the length of a bag, taken along reference line l-l of FIG. 3;

FIGURE 2 is a grossly exaggerated fragmentary front view of the bag of FIG. 3, with a serrated edge lip viewed from the opening end;

FIGURE 3, in perspective, shows a bag, laying flat, having a serrated or scalloped edge along its opening;

FIGURE 4 is a grossly exaggerated fragmentary crosssectional view through the length of a bag, taken along reference line 44 of FIG. 5;

FIGURE 5, in the same kind of illustration as in FIG- URE 3, shows a bag with a raised bead edge along its opening.

Looking at FIGURES 1-3, it is seen that the bag B is formed from two overlying sheet portions, one being generally coextensive with and joined along its extremities with the other except along one edge thereof where a front opening 0 and a foldovcr flap portion F are formed. Flap portion F is folded to close and seal the bag. A scallop (or wave or curl) S is formed along the aforementioned edge and is advantageously of an overall deformed height (measured from each side of the plastic film) at least about A to /2 the thickness of the film in the bag. Actually, the height of the deformation in the scallop S can be as great as the thickness of the film in the bag and even two to three times this amount.

The scalloped edge 8 can be made along the edge of the bag by simple mechanical deformation procedures,

such as by running the bag edge through fluted rolls or squeezing it between dies adapted for the purpose. Of course, the scalloped portion can be set back from the edge any desired distance so long as contact is effected by the flap portion F in closing the bag. Generally, however, it is best to have the serrated lip S right at the edge of the opening.

The width of the deformation at the bag edge is not particularly critical, suitable results being had when it extends between about and inch from the edge into the bag body, although, if wanted, wider deformations can be employed.

FIGURES 4 and 5 demonstrate a bag in which the edge deformation is achieved by a beaded portion R made by folding over (and, generally with better results, adhesive or heat-sealing the folded strip) the opening edge opposite the flap portion F of the plastic bag B. While a beaded edge made in this way is generally of a double film thickness, single or triple folds can be employed. The same widths as for scalloped edges can be used in the beaded edge R. It makes little difference whether the bag is turned inside or outside in order to form the beaded edge R although preferably such edges are made with an inside turn.

In these bags, the wave or bead deformation at the edge of the opening breaks down the smooth surfaces at the closure to enable easier opening of the bag during its use in packaging operations. A beaded edge, such as shown in FIGURES 4 and 5, also results in greater seal strength in the opening of the-bag.

The bags of the present invention can be handled, filled, closed and sea-led in the same way as other bags of the same general type excepting that the present bags bring about the above-noted significant benefits.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications, especially in dimensions and locations, can be made therein without departing from the spirit and scope of the invention.

I claim:

1. A plastic film bag having one sheet portion overlying another sheet portion, said one sheet portion being generally coextensive with and joined along its extremities with said other sheet portion except along one edge thereof, the extremity of said one edge of said other sheet portion extending beyond the corresponding edge of said one sheet portion to form a flap, said edge of said one sheet portion being adapted to lie flatly upon and against said flap but being separable therefrom to provide an opening for said bag, and a linearly extending protuberant physical deformation formed along said edge entirely across said opening to render said edge readily separable from said flap.

2. The bag of claim 1, in which said physical deformation is in the form of a scallop contiguous with said edge.

3. The bag of claim 1, in which said physical deformation is in the form of a raised bead contiguous with said edge.

References (Iitcd in the file of this patent UNITED STATES PATENTS 2,056,804 Potdevin Oct. 6, 1936 2,334,600 Boysen Nov. 16,1943 2,488,212 Lloyd Nov. 15, 1949 2,778,173 Taunton Jan. 22, 1957 2,873,566 Sylvester et al Feb. 17, 1959 2,920,670 Mohlmann J an. 12, 1960 

1. A PLASTIC FILM BAG HAVING ONE SHEET PORTIN OVERLYING ANOTHER SHEET PORTION, SAID ONE SHEET PORTION BEING GENERALLY COEXTENSIVE WITH AND JOINED ALONG ITS EXTREMITIES WITH SAID OTHER SHEET PORTION EXCEPT ALONG ONE EDGE THEREOF, THE EXTREMITY OF SAID ONE EDGE OF SAID OTHER SHEET PORTION EXTENDING BEYOND THE CORRESPONDING EDGE OF SAID ONE SHEET PORTION TO FORM A FLAP, SAID EDGE OF SAID ONE SHEET PORTION BEING ADAPTED TO LIE FLATLY UPON AND AGAINST SAID FLAP BUT BEING SEPARABLE THEREFROM TO PROVIDE AN OPENING FOR SAID BAG, AND A LINEARLY EXTENDING PROTUBERANT PHYSICAL DEFORMATION FORMED ALONG SAID EDGE 